This shared resource supports 2 functions: patient sample repository and specialized flow cytometry. The epository functions of the core include the acquisition of appropriate patient samples, isolation and cryopreservation of mononuclear cells, separation and storage of plasma or serum, maintenance of a database annotating patient samples and distribution of samples to program investigators. We will safeguard patient privacy by ensuring that all samples are de-identified and are assigned coded unique identifying numbers. We will also verify compliance with our internal regulatory policies which stipulate that samples may be obtained and studied only from patients who have signed an IRB approved informed consent document. The flow cytometry functions of the core include multiparameter analysis of heterogeneous samples and high-speed cell sorting to obtain highly purified populations of defined progenitor populations. The specific aims of this core are listed below: 1. To ensure the maintenance of patient privacy and to verify that informed consent has been obtained for acquisition and study of all samples. 2. To ensure the acquisition of appropriate samples as designated in clinical research protocols carried out by program investigators. 3. To isolate and cryopreserve mononuclear cells and plasma or serum components from patient samples for subsequent study by program investigators. 4. To maintain an annotated database containing pathologic, cytogenetic and molecular information for clinical samples obtained from patients with myeloid leukemias. 5. To ensure that samples are distributed in a timely and equitable fashion to laboratory investigators for experiments proposed in this application. 6. To provide specialized multi-parameter analysis and high-speed cell sorting to obtain highly purified populations for functional and genetic analysis